HSC Survey Results

German Bank Survey # 7 Results from 24/10/2023

Survey Details

8 commercial purse seiners conducted this fishing survey on 24/10/2023 starting at 19:00:00.

Six of the eight vessels ran two transects in the German Bank box and one transect in the Seal Island Box. Brunswick Provider had problems completing their lines, and therefore their third line was run by Morning Star.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Since no fish were caught, no samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 11,184mt, and with turnover applied 5,502mt. The preliminary biomass estimate for Seal Island is 1,006mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2023-10-24 23:49:29 2023-10-25 02:11:35 -66.392 43.565 -66.392 43.231 GB 37.15 8.47
BP T02 2023-10-25 02:42:32 2023-10-25 05:04:06 -66.258 43.232 -66.257 43.566 GB 37.34 8.55
C1 T01 2023-10-24 23:03:48 2023-10-25 01:29:56 -66.491 43.565 -66.492 43.236 GB 39.28 8.71
C1 T02 2023-10-25 02:00:38 2023-10-25 04:25:15 -66.359 43.234 -66.359 43.566 GB 40.42 9.06
C1 T03 2023-10-25 05:00:38 2023-10-25 06:49:55 -66.230 43.501 -66.231 43.248 GB 30.36 9.00
FM T01 2023-10-25 00:10:42 2023-10-25 02:23:03 -66.426 43.556 -66.425 43.235 GB 36.70 8.98
FM T02 2023-10-25 02:55:21 2023-10-25 05:13:36 -66.291 43.234 -66.291 43.565 GB 38.20 8.95
FM T03 2023-10-25 05:49:30 2023-10-25 07:30:26 -66.169 43.500 -66.170 43.262 GB 27.47 8.82
LB T01 2023-10-24 22:55:13 2023-10-25 01:25:49 -66.477 43.566 -66.477 43.235 GB 38.19 8.22
LB T02 2023-10-25 02:02:16 2023-10-25 04:37:47 -66.343 43.229 -66.341 43.565 GB 38.96 8.12
LB T03 2023-10-25 05:18:37 2023-10-25 07:03:04 -66.217 43.502 -66.215 43.250 GB 29.07 9.02
LJ T01 2023-10-24 23:15:53 2023-10-25 01:40:03 -66.375 43.566 -66.375 43.234 GB 36.96 8.31
LJ T02 2023-10-25 02:12:57 2023-10-25 04:28:29 -66.240 43.233 -66.240 43.563 GB 36.69 8.77
LJ T03 2023-10-25 05:04:01 2023-10-25 06:47:03 -66.126 43.502 -66.125 43.249 GB 28.06 8.82
LM T01 2023-10-24 22:53:25 2023-10-25 01:19:43 -66.460 43.566 -66.458 43.233 GB 37.71 8.35
LM T02 2023-10-25 01:51:23 2023-10-25 04:14:16 -66.325 43.232 -66.325 43.566 GB 37.84 8.58
LM T03 2023-10-25 04:51:58 2023-10-25 06:51:48 -66.200 43.504 -66.202 43.233 GB 30.81 8.33
MS T01 2023-10-24 23:04:11 2023-10-25 01:21:01 -66.443 43.558 -66.443 43.239 GB 37.86 8.96
MS T02 2023-10-25 01:57:48 2023-10-25 04:17:48 -66.307 43.239 -66.307 43.565 GB 40.08 9.27
MS T03 2023-10-25 04:55:15 2023-10-25 06:43:35 -66.184 43.506 -66.186 43.250 GB 30.83 9.22
MS T04 2023-10-25 07:02:46 2023-10-25 08:22:34 -66.141 43.273 -66.141 43.486 GB 25.87 10.50
SL T01 2023-10-24 23:50:17 2023-10-25 02:23:13 -66.409 43.573 -66.409 43.234 GB 40.38 8.55
SL T02 2023-10-25 02:54:32 2023-10-25 05:14:35 -66.275 43.234 -66.274 43.567 GB 40.65 9.40
SL T03 2023-10-25 05:50:04 2023-10-25 07:44:30 -66.155 43.501 -66.155 43.242 GB 31.40 8.89

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LB T02 -35.5 -50.579 0.031
FM T02 -35.5 -50.903 0.029
C1 T02 -35.5 -52.554 0.020
LJ T01 -35.5 -53.093 0.017
BP T01 -35.5 -53.120 0.017
LM T02 -35.5 -53.580 0.016
MS T01 -35.5 -54.392 0.013
MS T02 -35.5 -54.397 0.013
FM T01 -35.5 -54.428 0.013
LJ T02 -35.5 -54.992 0.011
SL T01 -35.5 -55.336 0.010
BP T02 -35.5 -55.619 0.010
LM T01 -35.5 -56.495 0.008
LB T01 -35.5 -57.198 0.007
C1 T01 -35.5 -57.405 0.006
C1 T03 -35.5 -57.669 0.006
LM T03 -35.5 -57.981 0.006
LJ T03 -35.5 -58.165 0.005
SL T02 -35.5 -59.327 0.004
LB T03 -35.5 -60.062 0.003
FM T03 -35.5 -61.531 0.002
SL T03 -35.5 -61.762 0.002
MS T04 -35.5 -62.060 0.002
MS T03 -35.5 -63.153 0.002
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 796 -54.0233 0.0141 11,183.581 NA NA 1,501.23 13.42
Seal Island -35.5 272 -59.8213 0.0037 1,005.621 NA NA 169.62 16.87
School Survey NA NA NA NA NA NA NA NA NA

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by LB, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LB, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2023-08-06 2,686.514 2,686.514 2022-08-14 16,285 16,285 22,081 22,081
German Bank 2 2023-08-20 4,930.454 4,406.486 2022-08-28 7,472 4,296 11,699 7,393
German Bank 3 2023-09-03 9,959.441 8,901.000 2022-09-11 12,507 10,464 11,902 8,826
German Bank 4 2023-09-13 16,265.846 13,203.000 2022-09-25 15,924 13,216 12,503 9,761
Seal Island 1 2023-08-06 1,205.361 NA 2022-08-14 2,598 2,598 2,086 2,086
Seal Island 2 2023-08-20 1,917.847 NA 2022-08-28 1,048 1,048 570 570
Seal Island 3 2023-09-03 2,062.584 NA 2022-09-11 6,941 6,941 6,392 6,392
Seal Island 4 2023-09-13 5,635.715 NA 2022-09-25 4,634 4,634 3,732 3,732
German Bank 5 2023-09-27 15,241.681 11,360.000 2022-10-10 19,539 16,337 20,247 17,675
Seal Island 5 2023-09-27 53,843.744 NA 2022-10-10 5,243 5,243 5,604 5,604
German Bank 6 2023-10-11 23,613.676 20,057.000 2022-10-23 13,399 8,684 15,565 10,823
Seal Island 6 2023-10-11 15,261.261 NA 2022-10-23 2,944 2,944 3,260 3,260
German Bank 7 2023-10-24 11,183.581 5,502.000 NA NA NA NA NA
Seal Island 7 2023-10-24 1,005.621 NA NA NA NA NA NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2022 German Bank 85,126.00 69,282 93,997 76,559
2022 Seal Island 23,408.00 23,408 21,644 21,644
2023 German Bank 83,881.19 66,116 NA NA
2023 Seal Island 80,932.13 NA NA NA

Tagging, Plankton, and CTD Data

Tag Data

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number GB2023-13 GB2023-14
Ground GB GB
Date 24/10/2023 24/10/2023
Wind Direction (km/h) NW NW
Swell (m) 0.5 0.5
Air Temp (c) 11 11
Tow Details
Tow Start 18:32:00 18:50:00
Tow End 18:42:00 19:00:00
Start Lat 43.57133 43.56983
End Lat 43.57183 43.57217
Start Lon -66.35683 -66.36250
End Lon -66.37028 -66.36917
Avg Tow Depth (m) 2.814608 6.030987
Speed 1.3 1.1
Heading 271 300
Tide Direction against against
Other Data Collection
Flow Start 645903 666985
Flow End 666985 680588
No. Revolutions 21082 13603
Distance (m) 566.5366 365.5534
Volume 1779.775 1148.386
Secchi Disappear (m) 5 5
Secchi Reappear (m) 4 4

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2023-13, which was against the tide and had an average depth of 2.8146076m. The second tow is GB2023-14, which was against the tide and had an average depth of 6.0309871m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2023 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.79. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.